Loss Exponent
In the study of wireless communications, path loss can be represented by the path loss exponent, whose value is normally in the range of 2 to 4 (where 2 is for propagation in free space, 4 is for relatively lossy environments and for the case of full specular reflection from the earth surface—the so-called flat-earth model). In some environments, such as buildings, stadiums and other indoor environments, the path loss exponent can reach values in the range of 4 to 6. On the other hand, a tunnel may act as a waveguide, resulting in a path loss exponent less than 2.
Path loss is usually expressed in dB. In its simplest form, the path loss can be calculated using the formula
where is the path loss in decibels, is the path loss exponent, is the distance between the transmitter and the receiver, usually measured in meters, and is a constant which accounts for system losses.
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